Thermal fire alarm system



1955 F. c. EVANS I 2,721,991

THERMAL FIRE ALARM SYSTEM Filed July 8, 1953 3 Sheets-Sheet 1 F I G I '2 KR- A 7 I w ALARM DEVISE i f2] I FIG.2

IN VEN TOR.

F. C. EVANS Ml/mm W)- ATTORNEY Oct. 25, 1955 F c. EVANS 2,721,991

THERMAL FIRE ALARM SYSTEM Filed July 8, 1953 3 Sheets-Sheet 2 FIG.3

INVENTOR.

F. C. EVANS ATTORNEY Oct. 25, 1955' F. c. EVANS THERMAL FIRE ALARM SYSTEM 5 Sheets-Sheet 3 Filed July 8, 1953 PIC-3.6

FIG.7

INVENTOR.

F. C. EVANS ATTORNEY United States Patent THERMAL FIRE ALARM SYSTEM Francis C. Evans, Dongan Hills, N. Y., assignor to American District Telegraph Company, Jersey City, N. J., a

corporation of New Jersey Application July s, 1953, Serial No. 366,716

9 Claims. or. 340-227 This invention relates to fire detection systems and more particularly to a system employing heat detecting devices such as thermocouples.

The present application is a continuation-in-part of U. S. application Serial No. 174,898, filed July 20, 1950, now Patent No. 2,678,433. The term thermocouple as used in the specification and claims is understood to include a literal thermocouple or a plurality of thermocouples making up a thermopile.

The premises in which a thermal fire detecting system is employed may include a local heating unit of the blower type in which heat currents are intermittently blown over premises. If such heat currents are of sufficient temperature, potentials may be developed by the alarm thermocouples of sufficient magnitude to actuate an alarm device. Consequently a compensating means may be provided to neutralize the effect of the local heating unit while at the same time maintaining the sensitivity of th system. 1

Accordingly, it is an object of this invention to provide an improved thermal fire detecting system.

Another object of this invention is to provide a fire detecting system wherein the effect of a local heating unit is compensated for.

Another object of this invention is to provide a fire detecting system that automatically compensates for the effect of a local heating unit and wherein the compensation may be controlled.

A further object of this invention is to provide a compensator means which will be unaffected by other than its associated heat source.

These and other objects will become apparent from the specification taken in view of the drawings in which:

Fig. 1 is a schematic diagram of a fire detecting system embodying the present invention;

Fig. 2 is a circuit diagram of a compensator unit;

Fig. 3 is a plan view of a compensator unit;

Fig. 4 is an elevational view of the unit of Fig. 2;

Fig. 5 is a section taken on the line 55 of Fig. 3;

Fig. 6 is a section taken on the line 66 of Fig. 3; and

Fig. 7 is a perspective view of a louver member.

Referring now to Fig. 1, thermocouples 11, 12, 13 and 14, conveniently located about the premises, are connected in series by conductor 15. Also in series with these thermocouples is a relay 16 and meter 17. The thermocouples are connected in additive relation so that an increase in temperature on the premises will be cumulative to produce a potential to energize relay 16 thereby closing its contacts. Relay contacts 16 complete a series circuit of battery 18 and alarm device 19.

The alarm thermocouples are of conventional construction and may comprise a plurality of hot and cold junctions of dissimilar metal arranged so that when the hot junctions are at a temperature higher than the cold junctions, a potential will be generated.

A blower heating unit 20 has a compensator unit 21 located adjacent thereto and connected in series with the alarm thermocouples. The polarity of compensator unit 21 is such as to oppose the potentials generated in the alarm thermocouples. It is seen, therefore, that heat currents emanating from heater 20 will cause a bucking potential to develop across the compensator unit 21 thereby neutralizing the potentials developed across the alarm thermocouples due 'to the heat currents from unit 20.

Referring now to Fig. 2, it is seen that compensator unit 21 comprises a plurality of bimetallic junctions 22 connected in series and to terminals 23 and 24. While four junctions are shown inFig. 2, it is of course understood that any number may be employed. Connected across terminals 23 and 24 is a rotary switch 25 including a rotary sweep 26 adapted to ride over a plurality of contacts. Connected across each adjacent pair of contacts is a resistor which may be of any practical value though one ohm has been found to be highly satisfactory. One contact of the rotary switch is left open. It is seen from the above that the setting of rotary switch 25 will determine the amount of resistance across the compensator thermocouple and consequently the etiectiveness thereof. Switch arm 26 may be positioned on the off contact thereby shunting out the compensator thermocouple or it may be set on the full position whereby the effectiveness of the thermocouple is maximum.

The compensator is adjusted by turning on heater 20 and setting switch arm 26 at a point where meter 17 gives a zero indication thereby indicating that the potentials developed by the alarm thermocouples due to heat source 20 are neutralized by the potential developed by compensator thermocouple 21.

Referring now to Figs. 3, 4, 5 and 6, the compensator unit is enclosed in a sheet metal housing comprising two sections. One section includes sides 27, 28, and bottom member 29. Each of these members has a forward extension integral therewith and flaring outwardly from the face of the unit. An upper flaring member 31 is suitably fastened to the extensions of side members 27, 28. Support bar 32 secured to the upper edge of the side members at the front end of the unit by welding or other suitable means is tapped to receive screws 33 and 34. L-shaped bracket 35 is fastened to bottom member 29 and receives screw 36. Louver members 37 pivot from small openings in the side members 27, 28.

The other section of the housing comprises sheet metal members 38, 39 integral with each other and at right angles. Member 38 has an opening to receive conduit coupling 40. Secured by screws 42 and nuts 43 to the underside of top member 38 is an insulated terminal block 41. The forward edge of member 38 has slots therein received by screws 33 and 34. A rotary switch 25 is secured to the inner face of back member 39 by support screw 44 and nut 45. The rotary switch 25 is of conventional construction and may be of the general type disclosed in U. S. Patent 2,177,481. The sweep arm 26 of switch 25 is operated by shaft 46 passing through member 39. Screws 47 and 48 secure thermocouple 21 to back member 39. Screw 36 passes through member 39 to secure the two sections of the housing together.

It is seen that the compensator unit is easily accessible by loosening screws 33, 34 and removing screw 36 to release the two sections of the housing. Back member 38 has two openings 51 and 52 therein. Baffles 53 and 54, which may be formed integral with member 39, extend upward at an angle to direct rising heat currents from openings 51 and 52.

The construction of the housing provides insulation for the compensator thermocouple from heat sources other than a direct blast of heated air from the front. A source of heat from the underside of the compensator unit producing rising heated air currents would be directed away'from" the compensator" thermocouple by baffles 53 and 54. Also, heat currentsfrom the face of the unit would be ineffective on the compensator thermocouple unless of sufiicient force to open louvers 37.

lt'is' seen; therefore, that the present invention providesa; compensator'unit'that willneutralize the heating" effect of its associated blower heater 'without beingafiecv ed by hostile fires, thereby maintaining maximum sensitivityof the'system.

While the-present invention has been disclosed by a specific embodiment, it is understood that this is not to be construed as limiting the invention as defined in the appended claims.

What is claimed is:

1.- A-compensator unit of the character described comprisingahousing made up of a first section and a second section,. said' first section including a bottom member, two side members and outwardly flaring members adapted to funnel air into the compensator, a plurality of louvers pivotedon said side members'forming a front panel for said compensator, means securing said first section to said 'second-section and a heat-responsive compensator element-within said housing.

2; A-compensator unit of the character described comprising :a housing made up of a first section and a second sectiomsaidfirstsection including abottom, two sides and: outwardly flaring members adapted to funnel air into said compensator, said second section including a top member and a back member, said back member having.atileast one opening therein, a bafile secured to-the back'member to direct rising heated air currents away' from said.opening,.means securing said first section to saidsecondsection, and a heat-responsive compensator element within said housing.

3. In a compensator unit for a thermal fire detecting system,.a housing comprising a bottom member, a top member, two side members, a back member and a face, said. face comprising a plurality of louvers pivotably mounted on said side members whereby a direct blast of heated air will be admitted to said unit and convection currents-will be excluded therefrom, said back member having one opening therein, a baffle secured to said back member to direct rising heated air currents away from said opening, and a compensator element within said housing. responsive to said blast of heated air.

4. In a compensator unit for a thermal fire detecting system,.a heat detecting device, a housing surrounding said device, a plurality of pivotably mounted members forming one face of said housing, a flat plate having a plurality of openings therein forming the opposite face of: said-housing, and a plurality of bafiles secured to said opposite face to direct rising heated air currents away'fromtsaid heat detecting unit.

5. In a: compensator unit for a thermalfire detecting system, a-housing comprising a first section andasecond section, said first section including a bottom member, two side members and outwardly flaring members adapt-- ed. to funnel air into said-compensator; a plurality of louvers pivoted on said side members whereby a direct blastof heated air willbe admitted to said unit, said second. section including a top member and a back member, said back member having at least one opening therein, abafiie secured to the back member to direct rising heatedair currents away from said'opening, means to securesaid first housing section to saidsecond housing section, and a heatv detecting device mounted in the housing;

6. Apparatus for compensating a fire alarm system against an intermittently-occurring directed'stream of" hot air from a friendly source of heat, comprising a housing in the path of said stream, normally closed, pivoted louvers forming at least a portion of one wall of said housing adjacent said source, a heat-responsive member within said housing for generating a compensating voltage to compensate said system for heat from said friendly source, said pivoted louvers serving normally to shield said heat-responsive member but being adaptedito open.

upon receipt of a stream of hot' air from said: friendly source to enable said hot air to actuate said heat-responsive member and cause it to generate said compensating voltage, and means interconnecting said heatresponsive member to the remainder of said system so that said compensating voltage may prevent said system from giving a false alarm in response to said stream of hot air from said friendly source.

7. A compensator unit for preventing a fire alarm system from giving a false alarm in response to a blast of heated air from a blower heater, said compensator unit comprising a heat-responsive device connected to the remainder of said system, said device being adapted, when heated, to compensate said system for the effect of said blower heater, and a housing surroundingsaid heat-responsive device and shielding same from hostile sources of heat, said housing having a front side adapted to be facedtoward said blast of heated air and located in the path thereof near said heater, said housing including on its front side normally-closed pivotally-' mounted louvers, said louvers being adapted to swing in wardly to an open position under the force of said heated air blast when it occurs, whereby said blast of heated air from said blower heater opens said louvers, enters said housing through same, and heats said heat-responsive device therein.

8. A compensator unit as in claim 7 in which said louvers are pivoted on a horizontal axis passing through an upper portion of said louvers, being thereby arranged so that gravity normally holds them closed and said heated air blast may blow them open and enter said housing and actuate said device therein.

9. A housing for a heat-responsive compensating element, for use in a fire alarm system of the typeincluding heat-responsive alarm-actuating devices spaced about the protected premises and a heat-responsive compensating element located in front of an intermittently-acting blower-heater for preventing false alarms when said' blower-heater delivers a blast of heated air into said premises, said housing surrounding and substantially completely shielding said element from air currents strik-- ing it on all sides except a front side adapted to face said blast of heated air, said housing including on said front side normally-closed, pivotally-mounted louvers adapted to swing to an open position under the force of said heated air blast when it occurs, thereby enabling said heated air from said heater to enter said housing and heat and actuate said compensating element therein, whereby said housing shields said element from hostile sources of heat but not from said blower heater.

References Cited in the file of this patent UNITED STATES PATENTS 2,347,830 Kiburz et al. May 2, 1944' 2,421,768 Volliazzo et al. June 10, 1947 2,432,145 Evans Dec. 9, 1947 2,473,940 Clark June 21, 1949 2,537,028 Cahusac et al. Jan. 9, 1951 

